1. Field of the Invention
The present invention relates to a roller bearing cage taken in, for example a lower, larger end called a rod xe2x80x9cbig endxe2x80x9d of a connecting rod in an engine and more particularly to a roller bearing cage of gate-like configuration in axial cross section, which has a radially inside projection to keep a roller in place.
2. Description of the Prior Art
As the modern engines are needed to get further higher in horsepower, the crankshaft for the powerful engines has to be made so as to stand up to further high-speed revolution. To cope with this, the crankpins are made integral with the crank webs to enhance the rigidity or stiffness of the crankshaft. Thus, high-compression, high-speed engines will impose very harsh conditions on the roller bearings that are fitted between the crankshaft and the connecting rod.
An example of conventional bearing cages is disclosed in Japanese Patent Publication No. 27526/1994. As shown in FIGS. 7 and 8, the prior bearing to be interposed between the big end 35 of the connecting rod and the associated crankpin 36 in the engine is a sort of needle bearing including a number of needle rollers 22 and a cage 21 made in a configuration resembling any gate in axial cross section. With the roller bearing cage recited earlier, the cage 21 is comprised of circular rims 23 and cage bars 24 to provide pockets 28. The cage bars 24 are each made radially thick at axially opposite end areas 25 thereof while radially reduced at an axial middle area 26 thereof. The radially thick area 25 of the cage bar 24 has radially inside prongs 27 disposed midway between axially opposing edges thereof to keep the rollers 22 against their radially inward escape out of the cage 21. On the slim middle area 26 of the cage bar 24, moreover, there are provided radially outside projections 32 extending circumferentially out of an outside circular surface 30 of the cage bar 24 to keep the rollers 22 against their radially outward escape from the cage 21. The radially inside prongs 27 are made by coining grooves 31 on the inside circular surface 29 of the radially thick area 25 of the cage bar 24 to extrude the material by plastic flow towards the associated pocket 6. In return for the radially inside prongs 27 there are left the circumferential grooves 31 that are each sunk radially outwards below the inside circular surface 29 of the radially thick area 25.
Another example of the roller bearing cage is disclosed in Japanese Utility Model Laid-Open No. 124353/1977. The prior roller bearing cage is also directed to the provision of a roller retainer to keep the rollers against their radially inside escape out of the cage. The roller retainer is made of radially inside retainer projections that are placed at radially inside circumferential edges of circular rims, with extending towards axially inside the cage.
Modern high-compression, high-speed engines increasingly need the bearing cage for the big end of the connecting rod, which can carry well the heavy load and bear the much higher rpm than previously thought.
The present invention has for its primary object to resolve the major problem as stated earlier, and to provide a roller bearing cage most available for bearings in, for example a rod big-end of a connecting rod in modern high-compression, high-speed engines and more particularly to a roller bearing cage that makes certain of keeping rollers against escape out of the cage, making fabrication thereof much easier, permitting large varieties of cages in size to be made with easy processing management, and further much favorable for the needle bearings, which can carry well a large load, with even weighing less under the harsh conditions imposed by high-compression, high-speed engines.
The present invention is concerned with a roller bearing cage in which a roller bearing cage comprising, a cage composed of a pair of circular rims spaced apart from one another in an axial direction and cage bars positioned circumferentially at a-regular intervals between the rims and made integrally with the rims to form a pocket between any two adjacent cage bars, and rollers fit in the pockets, one to each pocket, the cage bars being each composed of thick ends lying in axial opposition to each other to provide guide surfaces on which the roller rolls and a slim mid-portion extending between the thick ends to provide a recess, and the cage bars each having a radially outside projection on an outside circular surface thereof while a radially inside projection on an inside circular surface thereof to keep the associated roller against escape out of the cage, and wherein the radially inside projection is made in a way extending circumferentially at a circular edge on the thick end.
In an aspect of the present invention, there is provided a roller bearing cage in which the radially inside projection is formed by forcing only the circular edge on the thick end to move by plastic flow into such a shape as extending circumferentially out of an inside circular surface on the thick end into the pocket. In the roller bearing cage constructed as stated earlier, moreover, plastic deformation at the circular edge on the thick end is done by a coining roll that is forcibly urged against the circular edge on the thick end.
In another aspect of the present invention, there is provided a roller bearing cage in which forming the radially inside projection at a circular edge on the inside circular surface of the thick end contributes to lessening an axial length of the thick end, which provides the guide surface on which the roller rolls. For example, the axial length of any one of the axially opposing thick ends can be reduced to the extent accounting for only some 11% to 15% of the overall axial length of the pocket. That is to say, forming the radially inside projection to keep the roller against escape from the cage at just the circular edge on the thick end contributes to lessening the axial length of the guide surface on which the roller rolls, compared with the prior cage in which the radially inside projection lies midway between the lengthwise opposing edges on the thick end, thereby yielding a weight saving on the overall weight of the cage, helping provide the roller bearing cage that is fitter to stand up to the high-speed rpm of the engines.
In another aspect of the present invention, there is provided a roller bearing cage in which forming the radially inside projection at the circular edge on the inside circular surface of the thick end helps render the inside circular surface of the thick end larger in inside diameter, thereby making it possible to reduce a circular interval between any two adjacent pockets. This enlargement of the inside diameter defining the inside circular surface on the thick end makes it possible to lessen a circumferential width of the pocket that has been commonly cut by punching operation, and in doing so the pockets defined between any two adjacent cage bars are allowed to increase by about one to two in their number. This eventually results in the increase of the number of the rollers accommodated in the pockets in the cage, thus ensuring the increase of load capacity in the roller bearing cage itself.
In a further another aspect of the present invention, there is provided a roller bearing cage in which forming the radially inside projection at the circular edge on the thick end results in rendering the inside circular surface of the thick end larger in inside diameter, thereby making the thick end slim in thickness direction. That is to say, the expansion of the inside diameter at the thick end of the cage bar leads to making the thick end slim in thickness direction, and in doing so the roller bearing cage of the present invention could realize a weight saving on its overall weight, becoming fitter to stand up to the high-speed rpm of the engines than the prior cage previously known.
In another aspect of the present invention, there is provided a roller bearing cage in which the thick end of the cage bar is made either equal or unequal with rim in their radial thickness.
In a further another aspect of the present invention, there is provided a roller bearing cage that can serve as a needle bearing applicable to a big end of a connecting rod in an engine.
With the roller bearing cage constructed as stated earlier, the radially inside projection to keep the roller against radially inward escape out of the cage can be readily made at the circular edge on the thick end, which lies open to the recess. In other words, the edge on the thick end, compared with any other part, may be much subject to plastic deformation into the radially inside projection by the use of forming tools such as the coining roll.
Forming operation by the coining roll according to the present invention, moreover, is easy in process management to control the plastic deformation at any desired magnitude, thus making it possible to finish the radially inside projection with high accuracy. Gently plastic flow at the edge makes certain of the radially inside projection that may be kept from making uneven engagement with the roller, complying with the high-speed revolution of the bearings with less subject to failure of lubrication. Moreover, the plastic flow caused by the coining roll at the edge makes sure of simplification and high precision of the forming operation. The roller bearing cage constructed as stated earlier according to the present invention weighs less in itself and lessens the contact pressure that might occur between the inside circular surface in the rod big-end and the outside circular surface of the roller bearing cage due to the centrifugal force imposed by high-speed revolution, thereby effectively preventing lubrication failure and binding between parts, and treating further high-speed revolution of engines.
Other objects and features of the present invention will be more apparent to those skilled in the art on consideration of the accompanying drawings and following specification wherein are disclosed preferred embodiments of the invention with the understanding that such variations, modifications and elimination of parts may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.